What can teeth tell us about our prehistoric ancestors?

Our distant past is just that: the distant past. It’s this murky place that science is slowly filling in but the landscape still largely exists just on the periphery of our imagination, and it’s dominated by raw, somewhat violent natures.

Our distant past is just that: the distant past. It's this murky place that science is slowly filling in but the landscape still largely exists just on the periphery of our imagination, and it's dominated by raw, somewhat violent natures. And in this distant past, we've cast our ancestors with personalities and traits to match the depths of our imagination. They may be intelligent, but there's a raw, unrefined quality that draws a ragged line between modernity and the the past.

There's a diorama in the Hall of Human Origins at the American Museum of Natural History that seems to perfectly capture this tension between science and imagination. In this scene, a pair of H. erectus, possibly mates but at the very least partners, are crouched over a recent kill but something has attracted their attention: a predator approaches lured by the kill and the pair is caught—frozen forever— between attack and defense. Do they stand their ground and fight for the meal they have claimed? Or do they flee and possibly live to fight another day?

As science adds more data to this murky realm the pictures become clearer. And as scientific methodologies and technology advances, this data can add detail in interesting ways. Work emerging from Al Khiday, Sudan demonstates that dental plaque can tell us about the diets our distant ancestors. Yes, that kind of plaque. It turns out that it's common throughout all archaeological periods—we haven't been great about caring for our teeth—and the chemical compounds and microfossils found in the stuff you're flossing to remove can provide a record about what you've eaten if left to build over time to form a calculus. This is helpful in pre-agrarian societies, in particular, with regard to plant matter.

When we look at the time prior to the Neolithic agrarian revolution, dietary information is largely been guided by the physical remains found on or near archaeological sites, which means vegetation is questionable. We know that our ancestors were likely consuming protein, some of which was likely raw as evidence of cooking happens in more recent archeological periods. Of course, we can make broader general claims about dietary tendencies based on the wear and tear of teeth found onsite. So while we also know our ancestors were consuming vegetation, we’re limited in our assumptions by the supporting evidence we find within the context of the site. This means that we might know that antelope was on the menu based on the skeletal remains we uncover, but not necessarily spinach because plant matter leaves little behind. This kind of ambiguity can color the ways in which we think about and conceptualize the distant past—cue violent, brutish themes conjured by our imagination and sensationalized by media.

One of the three richest Late Meroitic graves identified at the cemetery, that of a young male. Credit: Donatella Usai/Centro Studi Sudanesi and Sub-Sahariani (CSSeS).

By evaluating the dentition of individuals in a cemetery in Al Khiday, Stephen Buckley and colleagues can add an additional dimension of consistency and clarity to our understanding of the Mesolithic, Early Neolithic and Meroitic periods in the Sudan. They’ve found both organic and inorganic matter within the dental calculus of the recovered skeletons, including starch granules, plant fibers, and micro-charcoal. In the pre-Mesolithic samples, the starch granules are small and appear intact, suggesting that they were subject to little processing. But the starch granules from the Neolithic period show signs of being exposed to heat: some are cracked in ways that suggest they were roasted, and others show signs of gelatinization, which indicates the cellular structure was just beginning to break down possibly in the presence of water.

Were our ancestors cooking? Definitely, though with varying degrees. The charcoal indicates fire and smoke were present in all periods at Al Khiday. While these elements can also be used for protection, the charcoal found in the Neolithic samples is higher than that found in the pre-Mesolithic samples, which is consistent with the known use of cooking during this and other periods. And the starch granules from the Neolithic bear relatable marks of exposure. The reduced change in starches from earlier periods can be attributed to shorter cooking times. The authors draw a parallel with the Hazda who cook their tubers just long enough to facilitate peeling and chewing, which means that the center of the tubers are often raw.

What were these mysterious starches? One was possibly purple nut sedge (C. rotundus). This is significant because this plant is most commonly found in moist, tropical environments, adding further weight to the evidence that the Sudan of today was not the same Sudan of the distant past (cue imagination here, but now with a bit of evidence to shape the picture). Buckley’s team has found chemical evidence supporting the ingestion of C. rotundus, but there’s also contextual support from other areas. It’s been linked to the diets of Wadi population in southern Egypt, about 1000 km north of Al Khiday, which adds plausibility that it was present at this site as well. The drawback is that no evidence of C. rotundus has been found in the fossilized fecal matter onsite. This might be explained by the ways in which it was consumed. If it was only lightly heated, as is supposed, it would have been chewed and a resulting mass of chewed fibers would have been spit out. These fibers definitely would not have survived through the fossil record.

This body of research demonstrates new spaces in which we can look to for data to enhance our understanding of the murky realm that constitutes prehistory. Teeth are tools. We use them for chewing to facilitate consumption, but we also use them to tear things or hold things. We do these things today, so our ancestors probably did them too. This has nothing to do with evolutionary theory and everything to do with practicality. We see this behavior in different animals as well. These types of activities may leave traces behind, and be recorded in the health of dental remnants we recover. Taken together with contextual information from the sites in which they are recovered, they can help reconstruct biographical and ethnographic experiences to help reduce the opacity of the distant past. It’s a reminder that evaluating the past should be a complete experience.

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